Method for sequestering ions in an environmental matrix

Abstract

Methods and systems are provided for treating a contaminated environmental medium. In one example, the treatment includes adding a first jarosite-group mineral to the contaminated environmental medium to form a wet mixture under a set of conditions. The set of conditions is maintained over a duration of time to expedite precipitation of a second jarosite-group mineral, the second jarosite-group mineral incorporating contaminant cations and contaminant anions into a structure of the second jarosite-group mineral. The first jarosite-group mineral is added in situ at a contamination site.

The invention claimed is: 
     
       1. A method for treating a contaminated environmental medium, comprising:
 adding a first jarosite-group mineral and water to the contaminated environmental medium to form a mixture under a set of conditions and maintaining the set of conditions over a duration of time to expedite ion substitution at the first jarosite-group mineral to precipitate a second jarosite-group mineral, the second jarosite-group mineral incorporating contaminant cations and contaminant anions into a structure of the second jarosite-group mineral, wherein forming the mixture includes adding the first jarosite-group mineral to the contaminated environmental medium in situ at a contamination site, and wherein the set of conditions includes a pH of the mixture below 3. 
 
     
     
       2. The method of  claim 1 , wherein adding the first jarosite-group mineral includes adding potassium-jarosite (K-jarosite) to the contaminated environmental medium. 
     
     
       3. The method of  claim 2 , wherein the contaminant cations are incorporated into the second jarosite-group mineral to convert at least 65% of the contaminant cations in the contaminated environmental medium into the second jarosite-group mineral, and wherein the second jarosite-group mineral is plumbojarosite. 
     
     
       4. The method of  claim 3 , wherein the contaminated environmental medium is soil, and wherein the contaminant cations are incorporated to convert 100% of the contaminant cations in the soil to plumbojarosite. 
     
     
       5. The method of  claim 1 , wherein the set of conditions includes a temperature and state of saturation of the soil, and the duration of time is between 8 hours and one week. 
     
     
       6. The method of  claim 1 , wherein forming the mixture includes mixing the mixture at ambient temperature, and wherein the mixture is at ambient temperature over the duration of time. 
     
     
       7. The method of  claim 1 , wherein the set of conditions includes maintaining a pH of the mixture at 2.5 over the duration of time. 
     
     
       8. The method of  claim 1 , wherein the set of conditions includes a temperature of the mixture, and maintaining the set of conditions for a duration includes maintaining the temperature up to 80° C. for a maximum of 16 hours. 
     
     
       9. The method of  claim 1 , wherein the set of conditions includes maintaining the wet mixture saturated with a solution of the first jarosite-group mineral over the duration of time. 
     
     
       10. The method of  claim 1 , wherein adding the first jarosite-group mineral to the contaminated environmental medium includes adding the first jarosite-group mineral to one or more of soil, sediment, water, waste, and radioactive waste. 
     
     
       11. A method for treating a site of contamination, comprising:
 adding water and potassium-jarosite to a contaminated medium at a contaminated site to form a mixture; and 
 maintaining the mixture at an acidic pH over a reaction duration to sequester contaminant ions by substituting potassium cations in the potassium-jarosite with the contaminant ions. 
 
     
     
       12. The method of  claim 11 , wherein the contaminated medium is soil and adding the potassium-jarosite to the contaminated medium includes tilling an upper layer of the soil, the upper layer being a top 3 to 6 inches of the soil, prior to adding the potassium-jarosite, and saturating the upper layer of the soil with water. 
     
     
       13. The method of  claim 12 , wherein the upper layer of the soil is either heated up to 80° C. or not heated, prior to adding the potassium-jarosite, and a heated or not heated temperature maintained during at least a portion of the reaction duration. 
     
     
       14. The method of  claim 12 , wherein adding the potassium-jarosite includes suspending the potassium-jarosite in water, adding the suspended potassium-jarosite to the soil, and adding an acid without sulfate to the soil. 
     
     
       15. The method of  claim 12 , wherein adding the potassium-jarosite includes suspending the potassium-jarosite in a ferric sulfate/sulfuric acid solution and adding the suspended potassium-jarosite to the soil. 
     
     
       16. The method of  claim 12 , wherein the potassium-jarosite is added at a ratio of 30:1 of the contaminated medium:potassium-jarosite by mass. 
     
     
       17. A method for removing contaminant ions from an environmental medium, comprising:
 seeding formation of plumbojarosite by adding a plumbojarosite precursor to the environmental medium in situ, at a site of the environmental medium, and promoting ion substitution at the plumbojarosite precursor; and 
 maintaining an acidic environmental medium pH while seeding formation of plumbojarosite and promoting substitution. 
 
     
     
       18. The method of  claim 17 , wherein the plumbojarosite precursor is potassium-jarosite, and wherein the potassium-jarosite is synthesized by heating an aqueous solution of potassium hydroxide and ferric sulfate hydrate. 
     
     
       19. The method of  claim 18 , wherein promoting ion substitution at the plumbojarosite precursor includes at least substituting potassium cations of the plumbojarosite precursor with lead cations.